Telephone-transmitter.



R. G. BROWNE.

TELEPHONE TRANSMITTER.

APPLICATION FILED APR. 26.1907.

Patented May 4, 1909.

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UNITED PATENT ()FFXGE.

RALPH 0. BROWN t l, ()h SALFItl, MASSACHUSETTS, ASSlGNOR TO JOHN ABBOTT, TRUSTEE, OF WINCHESTER, MASSACHUSETTS.

TELEPHONE-TRANSMITTER.

No. 920,424. Specification of Letters Patent. Patented May 4, 1909. Application filed April 26, 1907. Serial No. 370,341.

To (lilo/710171 it may concern: phragni b is supporte l to receive sound vi- Be it known that l, RALPH C. BROWNE, of brations entering through the mouth piece. Salem, in the county of E sex and State of indicates a solid back consisting of a Massachusetts,haveinventedcertainnewand yoke or bridge. the ends of which are atuseful lniprovemcnts in 'lclephone-Transtached to the front wall or cover a of the Go mitters, of which the following is a specicasing. This bridge or support serves as a lication. solid backing for the microphone or button This invention has relation to telephone as ordinarily. transmitters of the general character of The microphcnie orbutton comprises llat those illustrated in my application Serial retaining walls (Z (1. Both of these may be No. 313,578, tiled April 25, .1906, in which made of mica covered with a silk fabric, the currentis caused to traverse the resistalthough find it convenient to construct ance or active material transversely of the only one of them in that way, as indicated lines of pressure upon said material. As exat d. The wall (K may be fairly rigid and be plained in my said application, by einployformed of some suitable insulating material mg a very thin layer of granular carbon or such as hard rubber. These two walls are. i'esistancc material. 1 am able to introduce arranged in parallelism and are separated by ii the. subscribcfls loop a high resistance, annular spacer a, being held thereagainst by the coin'luctivity of which is easily increased annular rings c c, which are internally from mininuim to maximum to secure the threaded so as to be screwed upon the greatest possible variations in currcnt. In spacer e. my said implication, the electrodes are ar- The members 6 e c are formed of metal ranged substantially liorizontallz' and care and they constitute one of the electrodes. must be taken to maintain them in their When the parts (7 d c e c are secured ton'opcr positions, for if the chamber in the gather, they form a chamber for the recepnitton be not completely tilled with the tion of the active material which is prefergranular material, the dislmation of the ably granular carbon. The layer of active button, so as to bring one of the electrodes material is very thin although it is exagvertically above the other, will cause it to be gerated in the drawings for the sake of illuszzo out of electrical contact with the carbon. tration. To the front. wall 4 of the button According to my present invention, .1 prois cemented or otherwise secured a small disk pose to utilize two electrodes, one arranged jdraving a boss or pinf, to which the center substantially near the center of the button of the diaphragm is secured by a screw f and the other radially remote therefrom, Tothe resilient wall ll of the button, which and provide such a construction and ar is at the rear thereof, there is attached a mcralrgcmcnt so that. although the button is tallic disk g, having a pin or stud y), which is rotated about its central axis, nevertheless mounted in an insulating bushing 0, located the electrodes will always be in electrical in an annular llangc formed in the support c. contact with the resistance material. A metallic screw 7: is passed through the wall 40 Referring totheacctnnpanyingdrawings,- 1/ into the disk g to secure in place an elec- Figure 1 represents a button or microplwne trodc Ii. 'lhis electrode consists of a confor telephone transmitters embodying my cavo-convex disk, the edges of. which extend invention. Fiji. 2 represents the same. with into the mass oi active inatcria-l. 'lhc inner the parts separated, some of the parts being electrode It is concentric with. the outer clec- 45 shown in section. Fig. 3 represents a 1011- lrodc, and current passes from one to the gitudinal section through a transmitter emother in lines transverse to. the lines of presbodving the invontigm. Figs, 4 and 5 rep sureon the. active material. reseiit another embodiment of theinvcntion. As the diaphragm is vibrated by the 111'- Fig. 6 represents another embodiment of the tion of sound waves impinging upon it. the

ol) invention in which the electrodes are progranular carbon is compressed, by the movevided with points. mcnt of one of the retaining walls (that ato) Referring to the drawings and more parrelatively to the other wall (to wit, the tlexiticularly to Fig. 3, a transmitter is shown ble wall I). It is evidcnt thatthe walls may comprising a cup-like casing 1.1-, having a be reversed, and that a diaphragm, separate 35 cover a with a mouth piece a". The diafrom the llexible wall, neednot be used. For

instance in Figs. 4, 5, and 6, transmitters are shown in which the flexible wall itself is arranged in front and serves as a diaphragm.

In these figures It indicates the flexible wall or diaphragm, the edges of which are clamped inthe casing a of the transmitter so that it ma receive the sound waves directly upon it t rough the mouth piece (H. m indicates the rear wall or abutmentof insulating ma terial which is backed by the disk n of any suitable material. Between the walls or disks k and m is an annular member, frame, or spacer 0, to form a thin flat chamber for the layer of variable resistance material.

he annular member 0 is made of metal and serves as the outer electrode for the electric current. Attached to the inner face of the rear .wall in, any suitable way s the central electrode 19 to which is connected a conductor which forms part of thetransmitter circuit. The casing (1 which is of metal and which is in contact with the electrode 0 also forms a part of the sa d transmitter circuit. The electrodes 1) and 0 may be provided with focusing points as shown in 1? ig. 6.

In the various forms of the invention herein described, there is a thin layer ol" active material confined between parallel retaining walls of which one is flexible or resilient, and annular electrodes one substantially at the center of the layer, and the other a t the outer edge of the layer, said electrodes being substantially concentric.

It is evident that the invention may be embodied in various other l orms which will readily suggest themselves to persons skilled in the art.

, Having thus explained the nature ol the. invention and described a way of coustructing and using the same, although without attempting to set forth all of the forms in which it ma be made, orall of the modes of its use, I dec are that what 1. claim isz-- 1. A telephone transmitter cou'iprising parallel retaining'walls of which one is movable toward and from the other and the other tive material.

2. A telephone transmitter comprising a diaphragm to receive sound waves directly thereon, a rear wall parallel thereto, and supported indepemlently thereof, an abutment for the rear wall, a thin layer of active material coniined by said diaphragm. and.

said rear wall, and electrodes in electrical contact with said layer between the faces thereof and so arranged that the current between them traverses a path transverse to the lines oi? pressure ol the diaphragm on said material, said electrodes being separated a distance considerably greater than the thickness of the active material.

I). A telephone transmitter comprising a diaphragm adapted to receive sound waves directly thereon, a rear Wall parallel thereto, an abuti'nent for the rear Wall, a thin layer of active material confined by said diaphragm and said rear wall, a centrally arranged stationary electrode in contact with the said material and a ring-like. electrode at the edge of said. layer, said electrodes being in the planes of the said layer and being separated a distance greater than the thickness ol said active material.

in testimony whcreol I have allived my signature, in presence of two witness RALPH U. BROY'VNE.

\Yitiicsses MAuoUs B. MAY, l6. BAaeiucrnicu. 

